For example, if ρ=0.3 and there are J=5 multiple observations per subject and 100 subjects, the power based on these 100 subjects is equivalent to the power based on 100*5/(1+(5−1)*0.3)=227 subjects with only one observation per subject. Standard software packages for power/sample size calculation, for example, PASS(25), can then be used to calculation the power for the latter case (see Results).
